Overload coupling devices have been previously disclosed (FR-PS 1,330,335) where the connecting or carrier links are made of elastic material, such as rubber. This ensures that alignment deviations between the coupled shafts do not have any disadvantageous effects. At the same time, a certain degree of vibration adsorption is obtained. Furthermore, the elastic links have failure or breaking points which allow the disconnection of the shafts in case of an overload.
Couplings of this kind, however, can be utilized only where some degree of torsion between the shafts is permissible or where torsion does not cause any damage. Thus, this type of coupling cannot be used for drive equipment with alternating loads, where the driven machine element must at all times maintain the same angular velocity as the driving machine element. Also, it is not possible to exactly determine with reliability and precision the overload point at which the elastic carrier links are to fail. Countless driving devices, however, depend on this requirement. Finally, the disposition of the elastic links fractured or otherwise destroyed in the case of overload is not adequately effected in these couplings. It is to be expected that the broken pieces of the carrier links may slip between the advancing edges of the extension halves or other portions of the machine elements still rotating and pass the extension halves or other portions of the machine elements which have already come to a stop, thus damaging the coupling.